Dans cette thèse, des vitrocéramiques et composites à matrice verres ont été élaborés avec pour objectif principal d’étudier les interactions entre la fissure et les différentes inclusions. Dans un premier temps, la nucléation et la cristallisation volumique de sphérulites dans un verre du système BaO-Al2O3-SiO2 ont été étudiées. Puis, l’influence de la cristallisation sur l’élasticité, la dureté et la ténacité a été mesurée. Il est apparu une augmentation de ces propriétés suite à la cristallisation. Après dopage avec des oxydes de terres rares, le verre a été fonctionnalisé par l’apparition de cristaux phosphorescents à la surface du matériau. Dans un second temps, l’influence d’un différentiel de coefficient de Poisson (entre la matrice et les inclusions) sur la propagation d’une fissure a été étudiée. Pour cela des composites à particules et matrices vitreuses ont été élaborés par Spark Plasma Sintering (SPS) et étudiés par Double Cleavage Drilled Compression (DCDC). Il a été mis en lumière une déviation de la fissure quand cette dernière arrive à proximité des inclusions vitreuses dans le cas où le coefficient de Poisson de l’inclusion est inférieur à celui de la matrice. Une déviation de moindre importance a été observée dans le cas inverse. Enfin, des nanocomposites fonctionnalisés par des particules de magnétite (Fe3O4) et d’or ont été obtenus suite à un frittage SPS. Les propriétés apportées par ces particules ont permis le chauffage du matériau, respectivement, par induction et par irradiation laser. Dans le deuxième cas, après un traitement laser de 10 min, une cicatrisation partielle de fissures d’indentation a pu être observée. / In this thesis, glass-ceramics and glass matrix composites have been developed in order to study the interactions between the crack and the various inclusions. Firstly, the nucleation and volume crystallization of spherulites in a glass of the BaO-Al2O3-SiO2 system were studied. Then, the influence of crystallization on elasticity, hardness and toughness was measured. An increase of these properties due to crystallization was observed. After doping with rare earths oxides, the glass was functionalized by surface crystallization of phosphorescent crystals. Secondly, the influence of a Poisson’s ratio differential (between the matrix and inclusions) on the crack propagation was studied. For this purpose, glassy particulate glass matrix composites have been elaborated by Spark Plasma Sintering (SPS) and studied by Double Cleavage Drilled Compression (DCDC). A deviation of the crack in the vicinity of the glass inclusions has been identified in the case where the Poisson’s ratio of the inclusion is lower than the one of the matrix. In the opposite case, less important deviations were noticed. Finally, nanocomposites functionalized with magnetite (Fe3O4) and gold particles were obtained after a SPS treatment. The properties provided by these particles allowed the material to be heated, respectively, by induction and by laser irradiation. In the second case, after a 10 min laser treatment, a partial healing of indentation cracks could be observed.

O presente trabalho avaliou a formacao de tecido osseo ao redor de implantes osseointegraveis de titanio, apos realizacao de defeitos osseos, utilizando diferentes tipos de substitutos osseos. Foram utilizados 5 caes de raca indeterminada, os pre molares e molares mandibulares foram extraidos, passados 12 semanas, os caes foram submetidos a um novo procedimento cirurgico aonde foram realizadas as perfurações preconizados pelo fabricante dos implantes, o osso vestibular da mandibula foi desgastado ate que parte da perfuracao fosse exposta, os implantes entao foram colocados nas respectivas perfuracoes, ficando com 4 espiras expostas. Esses defeitos foram preenchidos aleatoriamente com Bioglass® 45S5, Biosilicato® , Osso autogeno, e sem nenhum material de preenchimento. 18 semanas depois da colocacao dos implantes os caes foram mortos e suas hemi-mandibulas contendo os implantes removidas e submetidas aos analises histologiaos e histomorfometricas, os dados obtidos foram submetidos ao teste de Kruskal-Wallis. A histologia dos 4 grupos estudados revelaram a presenca de tecido osseo maduro em contato com os implantes, porem sem ralacao direta com os vidros bioativos e osso autogeno. A porcentagem de contato osso implante, matriz ossea mineralizada ao redor da espira, e area de espelho, nao mostraram diferencas estatisticas significantes entre os 4 materiais testados. Os resultados indicam que a presenca de substitutos osseos nao interfere com a formacao ossea ao redor dos implantes nesse modelo experimental. E existe resposta tecidual muito semelhante entre o osso autogeno, Bioglass® 45S5 e Biosilicato. / The aim of the present study was to investigate the amount of bone formation on Ti implants in sites with intra-bony defects filled with different bone substitutes. Mandibular premolars and first molars were extracted from 5 dogs, and after 12 weeks 3 implants were bilaterally placed in sites with intra-bony defects and each implantation site randomly received the following treatment: Biosilicate®, Bioglass® 45S5, aoutologous bone or no treatment. At 18 weeks after implantation, the hemi-mandibles containing the implants were removed and processed for morphological and histomorphometric analysis. Data were submitted to Kruskal-Wallis and Fishers test. The histological sections of the 4 experimental groups exhibited mature bone tissue in contact with implants, but not related with bioactive glasses or autologous bone used. The percentage of bone-implant contact, mineralized bone matrix between implant threads, and mineralized bone matrix within mirror area in the treated or non-treated sites were not statistically different among the 4 experimental groups. These results indicates that the presence of the bone substitutes evaluated here did not interfere with bone formation on Ti implants in sites with intra-bony defects. In addition, tissue response to Biosilicate® was similar to that of Bioglass® 45S5 and autologous bone.

O presente trabalho avaliou os efeitos provocados pela laserterapia de baixa intensidade (LTBI) no \'lâmbda\' 780 nm, 30 mW de potência e tempo de exposição de 150 segundos, resultando em uma fluência de 112,5 J/\'CM POT.2\' e energia total de 4,5 J, sobre o comportamento osteocondutor da vitrocerâmica elaborada a partir do genérico do biovidro de composição: 45% \'SI\'O IND.2\', 24,5% \'NA IND.2\'O\', 24,5% \'CA\'O\' e 6% \'P IND.2\'O IND.5\' em perfurações ósseas em tíbias de ratos. O biovidro foi recozido em cuba de inox acima de sua temperatura de transição vítrea, a 620 graus Celsius por 30 minutos e mantido a 790 graus Celsius por 60 minutos, em seguida foi realizada a espectroscopia Raman para verificar a cristalinidade. Foram realizadas perfurações abaixo da tuberosidade da tíbia direita de 64 machos de ratos da raça Wistar (Rattus norvegicus albinus) na idade adulta. Os mesmos foram divididos aleatoriamente em 4 grupos sendo eles: um controle e três submetidos à procedimento experimental de implante e/ou irradiação laser de baixa intensidade. Em todos os grupos foram utilizados 16 indivíduos. Posteriormente, os animais de cada grupo foram subdivididos em dois subgrupos cada, de acordo com o tempo de vida antes da eutanásia, que ocorreu com 7 e 13 dias P.O. A análise das características das fibras colágenas para determinar a neoformação tecidual, bem como seu estado de maturação, foi realizada através de corpos de prova em forma de lâminas coradas com HE observadas à microscopia de luz comum para verificar a presença de células no foco de lesão, lâminas coradas com Picro Sirius sob luz polarizada a fim de verificar o estado organizacional e microscopia eletrônica de varredura, utilizando métodos técnico-experimentais para avaliar a interação do biomaterial com o tecido ósseo. Os valores de birrefringência demonstraram uma melhor organização tecidual dos grupos irradiados com ou sem o implante de vitrocerâmico (p < 0,05), os grupos com vitrocerâmico apresentaram o tecido mais difuso, até mesmo nas regiões mais centrais da lesão aos 13 dias. O vitrocerâmico estimulou a proliferação osteoblástica (p < 0,05), assim como a radiação laser (p < 0,01). Pode-se concluir que o vitrocerâmico utilizado apresenta capacidade osteocondutora e que a radiação laser acelerou o processo de reparo na presença ou não do vitrocerâmico. / The present study evaluated the effects caused by the low level laser therapy (LLLT) at \'lâmbda\' 780 nm, power of 30 mW and dose of 112.5 J/\'CM POT.2\' and total energy of 4.5 J on the behavior osteoconductor of the glass-ceramic drafted from generic of bioglass of composition: 45% \'SI\'O IND.2\', 24.5% \'NA IND.2\'O\', 24.5% \'CA\'O\' and 6% \'P IND.2\'O IND.5\' in drillings in tibia bone of rats. The bioglass was anneal in cuba of stainless above its glass transition temperature, to 620 Celsius degrees for 30 minutes and maintained at 790 Celsius degrees for 60 minutes, then was held to Raman spectroscopy to verify the crystallinity. Drillings were made below the tuberosity of the right tibia of 64 males of the race Wistar rats (Rattus Norvegicus Albinus) in adult age. They were randomly divided into 4 groups which are: a control and three underwent experimental procedure to implant and/or of low intensity laser irradiation. In all groups were used 16 individuals. Later, the animals in each group were further divided into two subgroups each, according to the time of life before euthanasia, which occurs with 7 and 13 days postoperative. The analysis of the characteristics of collagen fibers was conducted through: slides stained with HE seen the light microscopy, to quantify the presence of cells in the focus of injury, slides stained with Picro Sirius Red under polarized light to verify the organizational state, microscope electronic scanning, using technical experimental methods to evaluate the interaction of biomaterial with the bone tissue. The values of birefringence showed better tissue organization of groups irradiated with or without the implant of glass-ceramic (p < 0.05), the groups with glass-ceramic showed collagen fibers more diffuse, even in the most central of injury to 13 days. The glass-ceramic stimulated the osteoblast proliferation (p < 0.05) as well as laser radiation (p < 0.01). Thus it is possible to conclude that the glass-ceramic has osteoconductive capacity and that laser radiation accelerated the process of repairing in the presence or not of glass-ceramic.

O presente trabalho sugere a substituição da sílica comercial pela sílica obtida da casca de arroz como fonte alternativa para obtenção do dissilicato de lítio, material que pode ser utilizado em aplicações odontológicas. Para esse fim foram desenvolvidos materiais com estequiometria base de 33,33%mol. Li2O e 66,67%mol. SiO2 com e sem adição de óxidos complementares, visando à obtenção de vitrocerâmicas de maior tenacidade, por meio das duas fontes de sílica, comercial e da casca de arroz. Como caracterizações iniciais, foram realizadas difrações de raios X (DRX) para as misturas iniciais das matérias-primas antes e após a fusão para obtenção dos vidros. Para o caso dos materiais sem adição dos óxidos, a caracterização quanto à sua devitrificação, foi realizada por análise térmica diferencial (ATD), utilizando diferentes taxas de aquecimento e granulometrias, para ambas as fontes de sílica. Valores de temperatura de pico de cristalização (Tp), sem adição dos óxidos, ficaram na faixa de 640°C para os materiais de ambas as fontes de sílica. Também por ATD foi analisado o fenômeno de devitrificação dos materiais com adição dos óxidos. Além disso, para observar a existência de fases intermediárias no sistema, foram também realizadas análises por DRX com variação térmica. Para visualizar a alteração microestrutural, de acordo com a variação da temperatura de tratamento térmico (TT), fonte de sílica e influência dos óxidos, foram realizadas caracterizações por microscopia eletrônica de varredura (MEV). O comportamento citotóxico dos materiais frente às colônias celulares foi observado por meio do ensaio de citotoxicidade. As propriedades mecânicas, de acordo com as alterações das variáveis estudadas, foram obtidas por meio de cálculos de dureza e tenacidade à fratura por ensaio Vickers. Foram encontrados valores de tenacidade à fratura de aproximadamente 1,75 MPam1/2 para ambas as fontes de sílica, com adição de óxidos a 660°C (TT). Diante dos resultados obtidos é possível afirmar grande potencialidade na substituição da sílica comercial pela sílica da casca de arroz. / This work suggests the replacement of commercial silica by silica obtained from rice husk as alternative source for obtaining lithium disilicate material that can be used in dental application. The lithium disilicate as dental material is a glass-ceramic that has good mechanical properties and chemical stability. For these developments the materials have been obtained using stoichiometry of 33.33%mol. Li2O and 66.67%mol. SiO2, without complementary oxide addition or with, seeking better fracture toughness comportment, to both sources of silica, commercial and from rice husk. As initial characterization X-ray diffraction (XRD) was performed for the mixtures of materials before and after the fusion to obtain the glasses. For materials without oxide addition, the two materials developed were characterized for their devitrification, in other words, the transition from glass to glass-ceramic was observed by differential thermal analysis (DTA), using different heating rates and granulometries. Peak crystallization temperatures (Tp), to both silica sources, heat rate 10°C/min and 1mm of granulometry, was in average values of 640°C. The DTA was used to verify the devitrification in material with oxide addition too. In addition, to observe the possible formation of intermediate phases on stoichiometric system of lithium disilicate, were also carried out high temperature X-ray diffractomery (HTXRD). To view the microstructural changes occurring in the system, according to the variation of heat treatments temperatures (HT), silica source and oxides influence, characterizations were performed by scanning electron microscopy (SEM). The cytotoxic behavior of the materials in cell colonies was observed by the cytotoxicity test. Mechanical properties, Vickers hardness and fracture toughness, were determined by calculus, using Vickers test data. Values of approximately 1.75 MPam½ were obtained for both silica sources with oxide addition to 660°C (HT). Results obtained show great potential in the replacement of commercial silica by rice husk silica.

Du fait de leur grande qualité optique, les monocristaux sont largement utilisés dans le domaine de la photonique, pour l’émission laser de puissance, la conversion de fréquence,.... Les monocristaux sont toutefois limités par leur mode fabrication qui est lent et onéreux et par la difficulté d’obtenir des pièces de grandes dimensions. Les verres tellurites sont des candidats de choix en raison de leur réponse non-linéaire élevée, leur mise en forme aisée et leur faible coût de production. Toutefois, pour certaines applications nécessitant des effets non-linéaires de second ordre, les verres ne peuvent pas être utilisés en raison de leur isotropie optique. Au cours de cette thèse, nous avons donc entrepris l’élaboration de composites vitrocéramiques tellurites composés de cristaux non-centrosymétriques capables de générer un signal de seconde harmonique. Les composites sont élaborés par co-frittage SPS d’une poudre de verre et de cristaux. Nous nous sommes également intéressés à la réalisation de céramiques transparentes tellurites pour l’élaboration de cavités lasers de dimensions millimétriques. Les matériaux tellurites sont en effet des candidats intéressants en raison de leurs indices de réfractions linéaires élevées et leurs basses énergies de phonon qui favorisent les transitions radiatives. Les céramiques transparentes ont été obtenues par un procédé innovant de cristallisation complète et congruente du verre qui allie la facilité de mise en forme du verre et les propriétés de la céramique finale. Nous avons également mise en œuvre la réalisation d’une nouvelle céramique transparente tellurate (TeVI) par frittage SPS d’une poudre céramique broyée. Les composés tellurates ont l’avantage de présenter de basses énergies de phonons et des propriétés diélectriques micro-ondes intéressantes. / Owing to thier high optical quality, single-crystals are widely used in photonics, for high power laser, frequency conversion… However, single-crystals are constrained by their manufacturing process which is slow and expensive and because it difficult to obtain large parts. Tellurite glasses are ideal candidate due to their high nonlinear response, the easy glass shaping and their low manufacturing cost. Nonetheless, for some kind of applications requiring second order nonlinear effects, glasses can’t be used because of their optical isotropy. During this thesis, we undertook the elaboration of tellurite glass-ceramics composites consisting of noncentrosymmetric crystals able to generate second harmonic signal. Composites are elaborated by SPS co-sintering of a glass powder and crystals. We are also interested in the elaboration of transparent tellurite ceramics in order to make millimetric laser cavities. Indeed, tellurite-based materials are interesting candidates owing to their high nonlinear refractive index and their low phonon energy, which favors radiative transitions. Transparent ceramics have been fabricated by an innovative way, the full and congruent crystallization of glass which combines the easy glass shaping and the properties of the final ceramic. We have also developed the elaboration of a new transparent tellurate ceramic (TeVI) by SPS sintering of a crushed ceramic powder. Tellurate compounds have the advantage of showing low phonon energy and interesting microwave dielectric properties.

O presente trabalho avaliou os efeitos provocados pela laserterapia de baixa intensidade (LTBI) no \'lâmbda\' 780 nm, 30 mW de potência e tempo de exposição de 150 segundos, resultando em uma fluência de 112,5 J/\'CM POT.2\' e energia total de 4,5 J, sobre o comportamento osteocondutor da vitrocerâmica elaborada a partir do genérico do biovidro de composição: 45% \'SI\'O IND.2\', 24,5% \'NA IND.2\'O\', 24,5% \'CA\'O\' e 6% \'P IND.2\'O IND.5\' em perfurações ósseas em tíbias de ratos. O biovidro foi recozido em cuba de inox acima de sua temperatura de transição vítrea, a 620 graus Celsius por 30 minutos e mantido a 790 graus Celsius por 60 minutos, em seguida foi realizada a espectroscopia Raman para verificar a cristalinidade. Foram realizadas perfurações abaixo da tuberosidade da tíbia direita de 64 machos de ratos da raça Wistar (Rattus norvegicus albinus) na idade adulta. Os mesmos foram divididos aleatoriamente em 4 grupos sendo eles: um controle e três submetidos à procedimento experimental de implante e/ou irradiação laser de baixa intensidade. Em todos os grupos foram utilizados 16 indivíduos. Posteriormente, os animais de cada grupo foram subdivididos em dois subgrupos cada, de acordo com o tempo de vida antes da eutanásia, que ocorreu com 7 e 13 dias P.O. A análise das características das fibras colágenas para determinar a neoformação tecidual, bem como seu estado de maturação, foi realizada através de corpos de prova em forma de lâminas coradas com HE observadas à microscopia de luz comum para verificar a presença de células no foco de lesão, lâminas coradas com Picro Sirius sob luz polarizada a fim de verificar o estado organizacional e microscopia eletrônica de varredura, utilizando métodos técnico-experimentais para avaliar a interação do biomaterial com o tecido ósseo. Os valores de birrefringência demonstraram uma melhor organização tecidual dos grupos irradiados com ou sem o implante de vitrocerâmico (p < 0,05), os grupos com vitrocerâmico apresentaram o tecido mais difuso, até mesmo nas regiões mais centrais da lesão aos 13 dias. O vitrocerâmico estimulou a proliferação osteoblástica (p < 0,05), assim como a radiação laser (p < 0,01). Pode-se concluir que o vitrocerâmico utilizado apresenta capacidade osteocondutora e que a radiação laser acelerou o processo de reparo na presença ou não do vitrocerâmico. / The present study evaluated the effects caused by the low level laser therapy (LLLT) at \'lâmbda\' 780 nm, power of 30 mW and dose of 112.5 J/\'CM POT.2\' and total energy of 4.5 J on the behavior osteoconductor of the glass-ceramic drafted from generic of bioglass of composition: 45% \'SI\'O IND.2\', 24.5% \'NA IND.2\'O\', 24.5% \'CA\'O\' and 6% \'P IND.2\'O IND.5\' in drillings in tibia bone of rats. The bioglass was anneal in cuba of stainless above its glass transition temperature, to 620 Celsius degrees for 30 minutes and maintained at 790 Celsius degrees for 60 minutes, then was held to Raman spectroscopy to verify the crystallinity. Drillings were made below the tuberosity of the right tibia of 64 males of the race Wistar rats (Rattus Norvegicus Albinus) in adult age. They were randomly divided into 4 groups which are: a control and three underwent experimental procedure to implant and/or of low intensity laser irradiation. In all groups were used 16 individuals. Later, the animals in each group were further divided into two subgroups each, according to the time of life before euthanasia, which occurs with 7 and 13 days postoperative. The analysis of the characteristics of collagen fibers was conducted through: slides stained with HE seen the light microscopy, to quantify the presence of cells in the focus of injury, slides stained with Picro Sirius Red under polarized light to verify the organizational state, microscope electronic scanning, using technical experimental methods to evaluate the interaction of biomaterial with the bone tissue. The values of birefringence showed better tissue organization of groups irradiated with or without the implant of glass-ceramic (p < 0.05), the groups with glass-ceramic showed collagen fibers more diffuse, even in the most central of injury to 13 days. The glass-ceramic stimulated the osteoblast proliferation (p < 0.05) as well as laser radiation (p < 0.01). Thus it is possible to conclude that the glass-ceramic has osteoconductive capacity and that laser radiation accelerated the process of repairing in the presence or not of glass-ceramic.

This study indicate that the chemical inter-diffusion between the Cr-doped glass/glass ceramic and quartz (SiO2) influence the fluorescence properties of glass, mainly because of Cr4+ replacing by tetrahedral of Si4+. Cr4+ fluorescence intensity was reduced and its emission band was shifted to longer wavelength (red shift). We selected the SiO2-based glass composition: Mg2SiO4 glass-ceramic and reduced a ratio of SiO2 sintered into the ceramic powder. This paper used diffusion characteristics of quartz (SiO2) to compensate for reduced SiO2 in the ceramic powder. After diffusing with quartz (SiO2), ceramics powder changed into glasses. The intensity of fluorescence and the crystal field had been improved. The center of Cr4+ fluorescence is about 1100nm belonging to Cr4+:Mg2SiO4 crystal. The ratio of Cr4+ in Mg2SiO4 crystal/Cr4+ in MgO-SiO2 glass increases from 0.33 to 1.74. The goal is to develop a novel glass which is resistant to SiO2 inter-diffusion degradation during fiber fabrication, and provide the new fiber technology to avoid the influence of inter-diffusion This study provides new types of treatment: Laser induced crystallization. Laser heat-treatment can more quickly induce crystals in glass during seconds, than traditional heat-treatment which require several hours. This study also indicate that one step laser heat-treatment induce micro-crystals, but one step laser heat-treatment induce nano-crystals. We successfully produced nano-crystallization during seconds.

Microbeam radiation therapy (MRT) is a potential cancer therapy technique that uses an intense X-ray beam produced by a synchrotron. In MRT, an array of microplanar beams, called a microbeam, is delivered to a tumour. The dose at each centre of planar beams is extremely large (several hundred grays) while dose level in the valley between the peaks is below several tens of gray. Moreover, the width of each planar beam is typically 20 - 50 µm, and the distance from a centre of planar-beam to that of adjacent beam is 200 - 400 µm. For the latter reasons, the fundamental requirements for the dosimetry technique in MRT are (1) a micrometer-scale spatial resolution and (2) detection sensitivity at large doses (5 - 1000 Gy). No existing detectors can satisfy those two requirements together. The objective of the Ph.D. research is to develop a prototype dosimetry technique which fulfils the requirements for measuring the dose profile in the microbeam. The currently used approach relies on the indirect detection of X-rays; in which the X-ray dose is recorded on a detector plate, and then the recorded signals are digitized using a reader. Our proposed approach utilizes Sm3+-doped polycrystallites, glasses, and/or suitable glass-ceramics (though our approach is not limited to the use of Sm ion) for the detector plate, in which a valence reduction of Sm3+, that is the conversion of Sm3+ to Sm2+, takes place upon irradiation of X-rays. The extent of reduction is further read out using confocal fluorescence microscopy via the photoluminescence (PL) signals of Sm3+ and Sm2+. The work carried out throughout the course of the research includes the construction of confocal fluorescence microscopy, synthesis and characterizations of dosimeter materials, as well as application tests of our approach for measuring the dose profile of a microbeam used at synchrotron facilities -- Canadian Light Source (CLS), Saskatoon, Canada, European Synchrotron Radiation Facility (ESRF), Grenoble, France, and SPring-8, Hyogo, Japan. Further, the research has shown that 1 % Sm-doped fluoroaluminate glass is one of the best candidates for the type of dosimetric application. It has the dynamic range of ~1 to over 1000 Gy which covers the dose range used in MRT, excellent signal-to-noise ratio (large extent of Sm3+ → Sm2+ change), and excellent stability of recorded signal over time. The recorded signal in the detector is erasable by heating or exposing to light such as UV. Furthermore, with a use of confocal microscope, it has ability to measure the distribution pattern of dose over the cross-section of microbeam. Therefore, we believe that our approach is one of the most promising techniques available.

Mica based glass - ceramics have been produced by subjecting the glasses in the SiO2 , Al2O3 , CaO , MgO, K2O , and F system to a controlled heat treatment called crystallization. TiO2 was added into the batch in the amount of 1 wt% of the glass as nucleating agent. B2O3 additions in the amounts of 1, 2, 4 and 8 wt% of the glass have been made in the batch to see and evaluate the effects of B2O3 additions on the texture of the mica glass ceramics. Crystallization was accomplished in two steps, nucleation and crystal growth. Nucleation temperature was 650 &amp / #61616 / C. Crystal growth temperatures were 850 and 1000 &amp / #61616 / C. The time for holding the specimens at the temperatures was 8 hours. The X-Ray diffraction analysis revealed that resultant glass ceramics possessed not only synthetic fluormica crystals called phlogopite which provide machinability, but also wollastonite crystals which provide biocompatibility. The scanning electron microscopy examinations have indicated that the amount and distribution of the crystalline phases varied as a function of B2O3 content and heat treatment schedule applied.

O presente trabalho sugere a substituição da sílica comercial pela sílica obtida da casca de arroz como fonte alternativa para obtenção do dissilicato de lítio, material que pode ser utilizado em aplicações odontológicas. Para esse fim foram desenvolvidos materiais com estequiometria base de 33,33%mol. Li2O e 66,67%mol. SiO2 com e sem adição de óxidos complementares, visando à obtenção de vitrocerâmicas de maior tenacidade, por meio das duas fontes de sílica, comercial e da casca de arroz. Como caracterizações iniciais, foram realizadas difrações de raios X (DRX) para as misturas iniciais das matérias-primas antes e após a fusão para obtenção dos vidros. Para o caso dos materiais sem adição dos óxidos, a caracterização quanto à sua devitrificação, foi realizada por análise térmica diferencial (ATD), utilizando diferentes taxas de aquecimento e granulometrias, para ambas as fontes de sílica. Valores de temperatura de pico de cristalização (Tp), sem adição dos óxidos, ficaram na faixa de 640°C para os materiais de ambas as fontes de sílica. Também por ATD foi analisado o fenômeno de devitrificação dos materiais com adição dos óxidos. Além disso, para observar a existência de fases intermediárias no sistema, foram também realizadas análises por DRX com variação térmica. Para visualizar a alteração microestrutural, de acordo com a variação da temperatura de tratamento térmico (TT), fonte de sílica e influência dos óxidos, foram realizadas caracterizações por microscopia eletrônica de varredura (MEV). O comportamento citotóxico dos materiais frente às colônias celulares foi observado por meio do ensaio de citotoxicidade. As propriedades mecânicas, de acordo com as alterações das variáveis estudadas, foram obtidas por meio de cálculos de dureza e tenacidade à fratura por ensaio Vickers. Foram encontrados valores de tenacidade à fratura de aproximadamente 1,75 MPam1/2 para ambas as fontes de sílica, com adição de óxidos a 660°C (TT). Diante dos resultados obtidos é possível afirmar grande potencialidade na substituição da sílica comercial pela sílica da casca de arroz. / This work suggests the replacement of commercial silica by silica obtained from rice husk as alternative source for obtaining lithium disilicate material that can be used in dental application. The lithium disilicate as dental material is a glass-ceramic that has good mechanical properties and chemical stability. For these developments the materials have been obtained using stoichiometry of 33.33%mol. Li2O and 66.67%mol. SiO2, without complementary oxide addition or with, seeking better fracture toughness comportment, to both sources of silica, commercial and from rice husk. As initial characterization X-ray diffraction (XRD) was performed for the mixtures of materials before and after the fusion to obtain the glasses. For materials without oxide addition, the two materials developed were characterized for their devitrification, in other words, the transition from glass to glass-ceramic was observed by differential thermal analysis (DTA), using different heating rates and granulometries. Peak crystallization temperatures (Tp), to both silica sources, heat rate 10°C/min and 1mm of granulometry, was in average values of 640°C. The DTA was used to verify the devitrification in material with oxide addition too. In addition, to observe the possible formation of intermediate phases on stoichiometric system of lithium disilicate, were also carried out high temperature X-ray diffractomery (HTXRD). To view the microstructural changes occurring in the system, according to the variation of heat treatments temperatures (HT), silica source and oxides influence, characterizations were performed by scanning electron microscopy (SEM). The cytotoxic behavior of the materials in cell colonies was observed by the cytotoxicity test. Mechanical properties, Vickers hardness and fracture toughness, were determined by calculus, using Vickers test data. Values of approximately 1.75 MPam½ were obtained for both silica sources with oxide addition to 660°C (HT). Results obtained show great potential in the replacement of commercial silica by rice husk silica.